The invention relates to a compensator for connecting a first pipe socket to a second pipe socket that is spaced from the former and movable with respect thereto, comprising an inlet pipe which is coaxially fixed on the outlet opening of the first pipe socket and an outlet pipe which is arranged approximately coaxially to the inlet pipe and is spaced therefrom and is coaxially fixed on the inlet opening of the second pipe socket and a fabric compensator, which connects the inlet pipe and outlet pipe to one another, wherein all the aforementioned pipes allow dust-laden gas to flow through, in the direction from the first pipe socket to the second pipe socket.
In firing systems, such as thermal power station and waste incinerators, and all other applications in which hot gases are guided in pipes, the temperatures in each case of the pipes are very varied, depending on the particular operating state. As a result, thermally related displacements of the pipe in their longitudinal axes and transversely thereto occur.
An important exemplary embodiment is a large incineration system with a circulating fluidized bed system. In the circuit of the exhaust-gas return, the so-called cyclone downpipe runs from the cyclone to the trap, which discharges the returning ash. This return circuit cannot be constructed as a pipe system welded throughout, since it would then be cracked by the strongly different temperatures of the individual pipe regions in the different operating states and the different expansions effected thereby.
It is therefore necessary to divide up this circuit, it being necessary to produce a connection at the joining point but again between the two pipe sockets, which can compensate for the thermally related movements of the two pipe sockets.
In the prior art, pipe ends that are moveable somewhat with respect to one another are connected to one another by means of flexible fabric compensators, with are arranged in the manner of a bellows and consist of a textile material that can withstand the, under some conditions, very high operating conditions and at the same time is permanently flexible so that it compensates the movements of the two pipe sockets with respect to one another.
The German utility model document DE 1 760 997, Steinmüller, describes two flue-gas ducting pipe sockets, which are movable with respect to one another. In this case, only a movement in the axial direction of the two pipes is compensated. To this end the two pipe socket are plugged telescopically one inside the other along a short length. In the process, a narrow joint is produced between the two flue-gas pipes, which is covered by a multi-corrugated compensator. It is disadvantageous that only a movement of the pipes with respect to one another in an axial direction can be intercepted. A further, very considerable disadvantageous is that, in the case of a transition of the streaming from the narrow into the wider pipe, as well as in the reverse direction , the diameter changes suddenly, so that at this point turbulence in the flow develops, which leads to the deposition of solids, which can be entrained by the flowing gas.
In the prior art, German utility model GS DE 94 02 263, GFG, describes a fabric compensator that consist of multiple layers: Alternately with a layer of a “high-temperature insulation fabric”, a stainless steel fabric or a stainless steel foil is incorporated. By this means, the fabric compensator is resistant to very high temperatures and nevertheless is moveable in the longitudinal direction as well as transversely to the flue-gas stream. This fabric compensator is held by a metal ring in each case at its two ends and, by means of this ring, is fastened on the two gas-carrying pipe sockets.
The decisive disadvantage of this fabric compensation is that its layers are very thin, which leads to cooling within the compensator. A further problem is that the cross-section for streaming suddenly enlarges. If the two pipe sockets are very close together, the compensator even forms a pocket. If the flue gas carries entrained solids, such as ash, also termed an inert mass, this is very quickly deposited in the compensator, which is bulged out like a pocket. In addition, it is additionally cooled by the defective insulation in this area and thereby become lumpy and hardens.
In a typical application case, the ash components have a temperature of about 900 degrees Celsius, which is opposed by a wall thickness of the fabric compensator of less than 1 cm. By this means, a significant cooling is effected, which in the case of ash leads to caking, that is to say to sticking together of the individual ash components. In this manner, crust-like deposits occur within the compensator and, at its inlet and outlet area, can lead to damage of the compensator and blockage of the flue gas ducting in this area.
Since the compensator is generally part of a very large and very complicated system with very high operating costs, the failure costs in comparison to the investment sum for the compensator are in many cases extremely high.
Against this background, it is the object of the invention to develop a compensator that permits as far as possible laminar flow of the dust-laden gas within the compensator and which cools the flue gas as little as possible. As a solution, the invention teaches that a hollow cylindrical inlet guide plate is fastened close to the first pipe socket, the radius of which corresponds approximately to the internal radius of the first pipe socket.
The essential feature of the invention is thus that the inlet guide plate, which covers the greatest portion of the distance between the two pipe sockets and—to a first approximation—complements the inlet pipe and the outlet pipe inwardly to form a double-walled pipe. This double-walled pipe is only interrupted by the slit between the inlet pipe and outlet pipe, which, however, is outwardly covered by the flexible fabric compensator. Inwardly, the “double-walled pipe” is interrupted by the two joints between the inlet guide plate and the two pipe sockets. These two joints, however, are essential, since the two pipe sockets move with respect to one another due to different temperatures of the system components, specifically both in the longitudinal and transverse direction of the compensator.
The inlet guide plate according to the invention thus prevents radiant heat from the gas stream from acting unhindered on the inlet and outlet pipe and through the joint on the fabric compensator. As a result, the gas stream is not so strongly cooled, which reduce crusting due to the sticking together of ash components and other dust particles.
Another, even more important advantage is that the inlet guide plate, for the most part, keeps ash, dust and other solids from penetrating through the joints between the inlet pipe and the outlet pipe onto the inner side of the fabric compensator. That is in particular dangerous because the ash components cool and therefore can form a crust within the compensator, which can lead to the destruction thereof on movement of the two pipe sockets with respect to one another, and the resulting movement of the fabric compensator.
In one embodiment, the penetration of ash through the joint between the inlet guide plate and the first pipe socket is reduced by a nozzle, which is disposed in the outlet opening of the first pipe socket. Within this nozzle, the inner radius of the first pipe socket tapers, so that at the outlet of the socket the flow velocity of the gas is increased and thereby a subatmospheric pressure occurs in the gap between the nozzle and the inlet guide plate. This subatmospheric pressure counteracts the penetration of foreign bodies into the hollow chamber between the guide plate and the two pipes.
If small solid bodies and particles from the dust contained in the flue gas and the entrained ash have penetrated into the dead spaces, then they adhere particularly strongly to the walls of these dead spaces if they are electrostatically charged. This electrostatic charging falls as a result of the intensive and multiple contact of the particles with one another and with the walls of the pipe socket. For dissipating this electrostatic charge, good earthing of all particles that may come into contact with the particles is very effective. The electrical earthing must therefore have a lowest possible electrical resistance, that is to say must take place over the greatest possible conductor cross-sections. One possibility for earthing are separate earthing cables for each component. A common earthing cable may also be laid from component to component. Other metal earthing connections are also suitable, provided they have a low electrical resistance in the material and at the connecting points.
As a variant for further improvement of the insulation capability of the compensator, insulating materials can be introduced between the inlet guide plate and the two pipes, which must naturally withstand the maximum temperatures prevailing there.
It is just as practical to provide a heat insulator between the fabric compensator and the outer walls of the inlet pipe and outlet pipe.
The additional insulation material, however, cannot prevent hot gas penetrating through the joints between the inlet guide plate and the two pipe socket, and thereby solid particles also penetrating into the space between the inlet guide plate and the inlet and outlet pipe. For protection of the joint between the first pipe socket and the inlet guide plate, the invention proposes an optional nozzle.
To this end, there is disposed, on the outlet opening of the first pipe socket, a ring, the interior diameter of which at the inlet end corresponds to the diameter of the first pipe socket and then tapers to a nozzle in that the internal diameter further reduces towards the outlet.
The protective effect of such a nozzle is so good that no other protective measures are proposed in the region of the joint at the inlet side.
Without further protective measures, in the region, the inlet guide plate can be connected via a plurality of radially extending bridges to the inlet pipe. As connection, it is sufficient that the inlet guide plate lies thereon, for example with a collar and/or a shoulder. The advantage of this relatively loose connection is that relative movements are possible between the inlet guide plate and the bridges.
As an option, an additional support of the inlet guide plate in the region of the centre of the compensator is proposed, where an inlet ring is fastened on the inside of the inlet pipe, and in the profile of the compensator the distance from the outwardly disposed inlet pipe to the inwardly disposed inlet guide plate is for the most part bridged.
In addition to, or alternatively, the inlet guide plate can also be connected to this inlet ring, which is disposed on that side of the inlet guide plate that is more remote from the first pipe socket. Here, too, an appropriate alternative is that the inlet guide plate only lies on the inlet ring with a shoulder, a retaining angle or another similar continuation, because it is then relatively moveable with respect to the inlet ring.
To make the interior space between the inlet pipe and outlet pipe on the exterior side and the inlet guide plate on the interior side as large as possible, the invention prefers that the inlet pipe is fastened on the exterior surface of the first pipe socket and that the outlet pipe is connected to the outer surface of the second pipe socket. The exterior surface of the pipe socket thus also corresponds approximately to the exterior surface of the compensator. Only the additional fabric compensator projects beyond this line.
To also additionally protect the joint between the inlet guide plate and the second pipe socket against the penetration of solids from the gas, the invention proposes, as a further advantageous embodiment, fastening a hollow cylindrical outlet guide plate to the outlet pipe. An outlet ring bridges the distance from the outlet pipe to the interior surface of the second pipe socket.
The inner surface of this outlet guide plate ought to overlap the inlet opening of the second pipe socket in the axial direction of the compensator and therein always only assume a very low distance from the second pipe socket. To this end, the radius of the outlet guide plate must remain constant independently of its operating temperature. For this, the invention proposes that the outlet guide plate comprise contiguous or overlapping hollow cylindrical segments. To compensate thermally related length changes, either the joint between the individual segments or mutually overlapping segments slide further over one another or are drawn down by the adjacent segment by a corresponding portion, so that the radius of the entire outlet guide plate is not changed.
In the design, the radius of this hollow cylindrical outlet guide plate must be chosen so much greater than the radius of the inlet guide plate that it can only cover the inlet guide plate in the longitudinal direction of the compensator by a portion and still, in the case of movements of the two pipe sockets transverse to their longitudinal axis, does not impact against the inlet guide plate. The outlet guide plate is—as mentioned—fastened to the outlet pipe via an outlet ring. The outlet ring thus bridges the distance between the outlet guide plate and the outlet pipe.
The principal advantage of this additional outlet guide plate is that, irrespective of the axial distance between the two pipe sockets, the joint between the inlet guide plate and the second pipe socket is always sealed in the radial direction by the overlapping outlet guide plate, as a result of which the penetration of solids into the annular hollow space of the compensator is further retarded. A further advantage is that the heat of the gas stream is thereby also kept back.
To further reduce the penetration of solids from the smoke-laden dust, the invention propose that the relative size—internal diameter of the second pipe socket, starting from its inlet opening, tapers continually until it is reduced approximately to the radius of the inlet guide plate. As a result of this cone, a turbulence-free transition of the stream is achieved which—in a similar way to the nozzle in the inlet region—also further reduces the risk of penetration of foreign bodies for the gap between the inlet guide plate and the outlet guide plate.
To seal the joint between the inlet guide plate and the second pipe socket in the axial direction, too, as far as possible, in an alternative embodiment the inlet guide plate and the outlet guide plate can be connected to one another by means of a floating coupling guide plate. This coupling guide plate is displaceable with respect to one of the two guide plates in the longitudinal direction of the compensator and with respect to the other guide plate in the transverse direction of the compensator. By this means the path of solid bodies between the inlet guide plate and the first pipe socket, through along the inner wall of the outlet guide plate, is stopped, irrespective of the position in which the two pipe sockets are located with respect to one another.
Another advantage is that the heat radiation outwardly is to the greatest extent blocked and thereby the gas is only very slightly cooled.
As a further embodiment, the invention proposes that, in the—approximately radially extending—inlet ring, a protrusion surrounding it by 360 degrees is formed. This protrusion projects into a recess of the adjacent outlet ring, the profile of this recess being formed so as to be approximately complementary to the profile of the protrusion, however enlarged by the distance that is determined by the maximum movements of the two pipe sockets with respect to one another. As a result, two further walls are constructed as resistance to thermal radiation from the hot gas, which counteracts a cooling of the gas stream.
Nevertheless, the interior space between the inlet guide plate on one side and the inlet and outlet pipe, on the other side, cannot be sealed absolutely hermetically, since the two pipe sockets can move with respect to one another and therefore must also deform the compensator. It is therefore not to be entirely ruled out that solid bodies from the gas penetrate into these hollow spaces. Since in principle, however, relatively little material moves therein, they are also called “dead spaces”. Such a space forms between the first pipe socket, the inlet pipe, the inlet ring and the inlet guide plate.
Another dead space is generated by the combination of the second pipe socket with the outlet pipe, the outlet ring and the outlet guide plate. A third hollow space is formed approximately in the centre of the compensator profile between the fabric compensator, the inlet ring, the outlet ring and the coupling guide plate. If at least one of these hollow spaces is subject to barrier air, which is supplied via a pipe from the outside, foreign bodies penetrating through it are opposed by a further resistance.
In an extension of this arrangement, another pipe can be connected to the dead spaces, which is connected to a suction device. By this means foreign bodies that, despite all measures, have still entered the dead spaces can be sucked out continually or at intervals.
For an improvement of the effect of the compensator, it is appropriate that the pipe and/or the rings and/or the guide plates are lined with insulating material on the faces facing the dead spaces. The complementary space to the dead spaces is to be filled with insulation. By this means, the heat losses of the flue gas are reduced across the compensator, which—as mentioned above—is very advantageous since, in this manner, the cooling ash and slag components of a flue gas hardly form lumps.
Another further variant that retards the adhesion of small solid bodies to the surfaces of the compensator is that the pipes, the rings and the guide plates are made of electrically conductive material and are electrically conductively connected. By this means, the electrostatic charge of the guide plates is avoided, which otherwise noticeably increases the adhesion effect of the solid components of the gas.
In a further alternative embodiment, the inlet pipe and the outlet pipe—in addition to the fabric compensator—are additionally connected to one another by means of a flexible sealing element, which is disposed within the fabric compensator. Surrounded by the inlet pipe and the flexible sealing element and the outlet pipe and the fabric compensator, a pressure chamber is thus created, which can be placed under permanent superatmospheric pressure via the barrier-air connection. The fabric compensator is thereby decoupled from the pulsations in the contiguous dead space between the inlet ring and the outlet ring. The pulsations are thereby prevented from acting directly on the fabric compensator and setting it into a “fluttering” movement, which would result in rapid wear.
Instead, the pulsations are restricted as a breathing on the inner dead space between the inlet ring and outlet ring. Thus, two barrier-air circuits are formed, of which the innermost between the inlet ring and outlet ring breathes and the outermost is essentially subject to a constant pressure.
Both barrier-air circuits are accessible from outside via connections and can thus be supplied with barrier air.
For the application case of a compensator, in which the outlet pipe is principally movable only in the axial direction against the inlet pipe, the flexible sealing element only needs to be fastened on the inlet pipe or the outlet pipe, and then lies on the respective other pipe with a lip or similar.